Without further interference, the rotation will swing back and forth randomly. Therefore, the team also dipped two electrodes in the solution and allowed alternating current to flow. The alternating direction of tension altered the energy landscape experienced by the long DNA arms, making rotation in one direction more convenient through a mechanism known as a Brownian flashing ratchet.
Turn these passive devices into real drives. The micrographs show that under these conditions, each arm—though randomly shaking—always rotated in the same direction on average.
By itself, the nanoactuator does nothing more than overcome the resistance of the surrounding solution. “It’s like swimming: You’re moving forward and doing a lot of work that evaporates into the water,” Dietz says. But to prove that the motor could also do useful work, the researchers went one step further: They attached another strand of DNA to their rotor and left it coiled like a hairspring used to shift gears in a mechanical watch being used. Such a mechanism could help nanomachines store energy or pull other mechanical components, Dietz says.
For him, the motor is the first important proof that the principle works and that not only static nanosystems can be produced with the help of DNA origami technology, but also systems that can do work. “Of course I was very happy to publish our work in Nature,” says Hendrik Dietz. “For me, thinking directly about the next project is a catalyst for me.” After all, his chair has just been renamed from “Molecular Design” to “Molecular Robotics.” .
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